With liquid crystal display devices and other such image display devices equipped with a backlight, it is possible to moderate the backlight power consumption and improve the image quality of a displayed image by controlling the backlight luminance on the basis of the input image. Particularly, by dividing the screen into multiple areas and controlling the luminance of a backlight source corresponding to a given area on the basis of the input image within that area, further reduction in power consumption and higher image quality becomes possible. Hereinafter, a method of driving a display panel while controlling backlight source luminance on the basis of an input image within an area in this way will be designated “area active driving”.
With a liquid crystal display device conducting area active driving, RGB tri-color light-emitting diodes (LEDs) or white LEDs are used as backlight sources. The luminance of the LEDs corresponding to each area is computed on the basis of factors such as the maximum luminance value and mean luminance value of pixels within each area, and is given to a backlight driving circuit as LED data. In addition, display data (data for controlling the optical transmittance of the liquid crystals) is generated on the basis of this LED data and an input image, and this display data is given to a liquid crystal panel driving circuit.
According to a liquid crystal display device as above, suitable display data and LED data is computed on the basis of an input image, the optical transmittance of the liquid crystals is controlled on the basis of the display data, and in addition, the luminance of the LEDs corresponding to each area is controlled on the basis of the LED data. In so doing, an input image may be displayed on a liquid crystal panel. Also, in the case in which pixels within an area have low luminance, the luminance of the LEDs corresponding to that area may be lowered, thereby reducing the backlight power consumption.
Meanwhile, in order to resolve the problem of insufficient luminance during single-area lighting (the case in which only the LEDs corresponding to a given area are in a lighted state) for a liquid crystal display device that conducts area active driving, there has been proposed a per-area luminance correction, which lights not only the area to be lighted (the area to be lighted refers to the area whose LEDs would originally be lighted by single-area lighting), but also the LEDs corresponding to areas near the area to be lighted. Hereinafter, such a correction process will be designated an “LED blur process”. According to an LED blur process, the area to be lighted is additionally illuminated by light from nearby areas, thereby resolving the problem of insufficient luminance. Note that an LED blur process is disclosed in Japanese Unexamined Patent Application Publication No. 2009-198530, for example.